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13. (η5-CYCLOPENTADIENYL)TRICARBONYLMANGANESE(I)COMPLEXES

Submitted by PATRICK N. KIRK* and MICHAEL P. CASTELLANI*

Checked by MICHAEL RIZZOy and JIM D. ATWOODy

Since the initial preparation of (η5-C5H5)Mn(CO)3 by Fischer and Jira in 1954,1

many methods have been developed for the synthesis of this compound (oftenreferred to as “cymantrene”) and its C5 substituted derivatives.

2 Interestingly, eachof these preparations has at least one significant drawback from a preparativeperspective (e.g., thallium reagents, high pressures, poor yields, or reactants thatrequire significant preparative investment).

Surprisingly missing from this collection of preparative methods is thedirect reaction between commercially available Mn(CO)5Br and NaC5H5.This omission suggests that the reaction proceeds in poor yields, which isconsistent with our experience. In 1988, however, Smart and coworkers foundMnBr(CO)3(pyridine)2

3 to be an effective reagent in making a substitutedindacenylmanganese tricarbonyl complex.4 Here we take advantage of the factthat this pyridine complex also serves as an effective manganese startingmaterial for the high-yield syntheses of cymantrene and its derivatives suchas (η5-C5Me5)Mn(CO)3.

A. (η5-CYCLOPENTADIENYL)TRICARBONYLMANGANESE(I)

MnBr�CO�3�py�2 � Na�C5H5� ?DME® �η5-C5H5�Mn�CO�3 � 2py

�NaBr � DME

Procedure

A Schlenk flask equipped with a magnetic stir bar is charged under an inertatmosphere, with MnBr(CO)3(pyridine)2

5 (0.400 g, 1.1mmol) and Na(C5H5) ?DME6 (0.230 g, 1.3mmol), where DME� 1,2-dimethoxyethane. Dry, deoxygen-ated THF (10mL) is added and the flask is stoppered. After the mixture has beenstirred overnight, the THF is removed in vacuum, being careful to avoid loss of thevolatile product by placing the residue under a nitrogen atmosphere as soon as the

*Department of Chemistry, Marshall University, Huntington, WV 25755.yDepartment of Chemistry, University of Buffalo, Buffalo, NY 14260.

Inorganic Syntheses, Volume 36, First Edition. Edited by Gregory S. Girolami andAlfred P. Sattelberger. 2014 John Wiley & Sons, Inc. Published 2014 by John Wiley & Sons, Inc.

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mixture is dry. Against a counterstream of nitrogen, a water-cooled cold finger isinserted into the flask, which is then sealed and evacuated. The flask is warmed in a50°C water bath for 2 h. The flask is refilled with nitrogen, and the CpMn(CO)3product can be collected from the cold finger in the air. Yield: 0.165 g (73%).*

Properties

(η5-Cyclopentadienyl)tricarbonylmanganese(I) is a yellow, air-stable solid thatsublimes at room temperature. It dissolves in many nonpolar and moderately polarsolvents (e.g., hexane, toluene, CH2Cl2, and acetone). The solution IR spectrumdisplays ν(CºO) bands at 2024 (m, sh) and 1937 (s, br) cm�1 in dichloromethaneor 2029 (m, sh) and 1947 (s, br) cm�1 in hexane.7 The 1H NMR spectrum in CDCl3displays a singlet at δ 4.75.

B. (η5-PENTAMETHYLCYCLOPENTADIENYL)-TRICARBONYLMANGANESE(I)

MnBr�CO�3�py�2 � LiC5Me5 ® �η5-C5Me5�Mn�CO�3 � 2py � LiBr

Procedure

A Schlenk flask equipped with a magnetic stir bar is charged under an inertatmosphere with MnBr(CO)3(pyridine)2

5 (0.400 g, 1.1 mmol) and LiC5Me58

(0.18 g, 1.3mmol). Dry, deoxygenated THF (10mL) is added and the flask isstoppered. After the mixture has been stirred overnight, the THF is removed invacuum. Against a counterstream of nitrogen, a water-cooled cold fingeris inserted into the flask, which is then sealed and evacuated. The flask iswarmed in a 90–95°C water bath for 3 h. The flask is refilled with nitrogen, andthe (η5-C5Me5)Mn(CO)3 is collected from the cold finger in the air. Yield:0.158 g (52%).

Properties

(η5-Pentamethylcyclopentadienyl)tricarbonylmanganese(I) is a yellow, air-stable solid that sublimes at elevated temperatures. It dissolves in many nonpolarand moderately polar solvents (e.g., hexane, toluene, CH2Cl2, and acetone). Thesolution IR spectrum in dichloromethane displays ν(CºO) bands at 2002 (m, sh)and 1913 (s, br) cm�1. The 1H NMR spectrum in CDCl3 displays a singletat δ 1.88.

*The checkers carried out the sublimation by transferring the dried reaction residue to a separatesublimator. This extra step probably was responsible for the checkers obtaining a lower yield of 51%.

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Acknowledgment

P.N.K. thanks the West Virginia EPSCoR—Research Challenge Fund—forsupport in the form of a SURE Summer Fellowship.

References

1. E. O. Fischer and R. Jira, Z. Naturforsh. B 9, 618 (1954).2. (a) P. M. Treichel, in Comprehensive Organometallic Chemistry, G. Wilkinson, F. G. A. Stone, and

E. W. Abel, eds., Pergamon Press, Oxford, 1982, Vol. 4, pp. 123–132; (b) P. M. Treichel, inComprehensive Organometallic Chemistry II, E. W. Abel, F. G. A. Stone, and G. Wilkinson, eds.,Pergamon Press, Oxford, 1995, Vol. 6, pp. 109–115.

3. G. E. Herberich, U. Englert, B. Ganter, and M. Pons, Eur. J. Inorg. Chem. 979 (2000).4. W. L. Bell, C. J. Curtis, A. Miedaner, C. W. Eigenbrot Jr., R. C. Haltiwanger, C. G. Pierpont, and

J. C. Smart, Organometallics 7, 691 (1988).5. M. Pons and G. E. Herberich, Inorg. Synth., 36, 148 (2014).6. J. C. Smart and C. J. Curtis, Inorg. Chem. 16, 1788 (1977).7. D. J. Parker and M. H. B. Stiddard, J. Chem. Soc. A 2263 (1968).8. J. M. Manriquez, E. E. Bunel, and B. Oelkers, Inorg. Synth., 31, 214 (1997).

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